Apparatus for preparing a material for high pressure deliquification

ABSTRACT

A belt filter press having a wedge zone which can be adjusted during operation of the filter press to prepare a sludge or other material to be deliquified in the most efficient manner for high pressure deliquification also includes a sealing arrangement for sealing the marginal edges of the upper and lower belts, a tapered slide cam assembly on either side of the belts for adjusting the wedge angle in a controlled manner, rack and pinion assemblies associated with hydraulic cylinders on either side of the belts to ensure the uniform movement of the lower belt supports, and the staggered arrangement of upper and lower belt support members where the lower belt support members are concave-like in shape to facilitate the sealing of the marginal edges of the belts, as well as to form a confined pocket which will facilitate the shearing action induced in the material to be deliquified.

This is a continuation of application Ser. No. 08/174,037, filed Dec.28, 1993, now U.S. Pat. No. 5,456,832.

BACKGROUND OF THE INVENTION

The present invention relates generally to filter presses for separatingliquids and solids in sludges, slurries and other feed materials, andmore specifically to presetting the thickness and consistency of suchmaterial in the wedge zone prior to advancing the material into a higherpressure zone.

Belt filter presses are used to separate liquids (most often water) andsolids in sludges, slurries, fiber suspensions, cellulose or otherfibrous materials and similar substances. The materials to be dewateredor deliquified could be sewage, industrial waste, paper pulp or anyother biological, chemical, mineral-based or industrial materialrequiring deliquification. The term "sludge" will be used herein torefer to any substance which might require deliquification. The need todeliquify a substance can range from a desire to dry a substance forincineration (so that less fuel is used during the incineration process)to simply removing excess liquid prior to transportation (in order todecrease transportation costs). Since all sludges differ from oneanother in consistency, viscosity, density, water content and many otherparameters, separating the liquids from the solids in sludges is acomplex art.

Belt filter presses can employ several stages at which differenttechniques are used to remove the liquid from a sludge. The use of thesedifferent stages improves filtering efficiency throughout the beltfilter press. Even prior to commencing liquid removal, a suspension,which might only be one half to one percent solids, can be treated Witha polymer or other chemical which coagulates or flocculates the solids.In a typical belt filter press, the flocculated sludge is then movedinto a gravity drainage section or stage of the belt filter press wherethe sludge is stirred and churned so that free water drains off bygravity. At the end of the gravity drainage zone, the sludge could benear 10% solids. The gravity drainage stage is used primarily to removefree water, and to prepare the sludge for, in some cases, a suctionstage where additional water is suctioned off and/or a low pressurestage which continues to prepare the sludge for higher pressure stagesof deliquification. It is at the higher pressure stages that the sludgeis carried between an upper and a lower belt which together follow apath between progressively smaller perforated drums, and finally betweenprogressively smaller solid rollers. While the pressure in the drum areamay be considered to be a medium pressure, for purposes of thisapplication, the perforated drum stage will be considered part of thehigh pressure stage.

As those in the art can appreciate, the pressure imparted to thematerial between the upper and lower belts in the high pressure stageincreases greatly from the largest perforated drum to the smallest solidroller. After completing travel through the high pressure stage, theupper and lower belts separate from one another, and the dried sludge orcake, which can typically be 30% solids, is discharged.

To more efficiently prepare a sludge for the high pressure stage, awedge zone is often interposed between the gravity drainage stage,suction stages, etc. and the high pressure stage. The result is greaterdeliquification in the high pressure stage since the wedge zone preparesthe sludge for the application of higher pressures. In the wedge zone,the upper belt and the lower belt (carrying the sludge therebetween)converge with one another, applying light pressure to set the thicknessand consistency of the sludge prior to reaching the largest perforateddrum. Light dewatering or deliquifying continues to occur in the wedgezone as the sludge is compressed between the belts. The degree to whichthe sludge is compressed corresponds to the angle of convergence of thebelts or the wedge angle. The wedge angle may be fixed at all times ormechanically adjusted prior to running the filter press to accommodate aparticular sludge. Applicants are aware of no commercial filter pressthat provides a wedge zone which is continuously adjustable while thefilter press is operating to deliquify a material. Wedge zones are shownin U.S. Pat. No. 4,181,616 to Bahr, U.S. Pat. No. 3,894,486 toSparowitz, U.S. Pat. No. 4,053,419 to Pav, U.S. Pat. No. 4,584,936 toCrandall and U.S. Pat. No. 4,681,033 to Crandall.

The advantages obtained by employing a wedge zone depend upon the extentto which the sludge can be deliquified and preset in a particular wedgezone, and thus relate to the amount of pressure that can be applied tothe sludge in the wedge zone. If too much pressure is applied in thewedge zone, the wedge angle being very small, rapid compression of thesludge occurs, resulting in the migration of the sludge beyond themarginal edges of the belts. If this occurs, very little stable sludgewill be delivered to the first perforated drum. On the other hand, ifthe pressure in the wedge zone is too low, the wedge angle being toolarge, not enough deliquifying occurs in the wedge zone, and the sludgeis not fully and evenly distributed across the belts and is too wet whenit reaches the first perforated drum. This results in the migration ofthe wet sludge from the sides of the perforated drum.

Therefore, there is a need for an apparatus for adjusting, in acontrolled manner, the wedge angle and thus the wedge pressure in thewedge zone during operation of the belt filter so that a sludge can beefficiently deliquified and properly preset prior to entering the highpressure stage.

Another way in which a sludge can be more efficiently deliquified in awedge zone is to solve the problem of migrating sludge beyond themarginal edges of the belts. If the marginal edges of the belts aresubstantially sealed, the sludge can bear a greater wedge pressurewithout migrating through the substantially sealed marginal edges. Thus,there is also a need to provide practical sealing means for the marginaledges of the belts.

Still further, while known wedge zones increase the efficiency of thedeliquification of the sludge, improvements in the inducement of shearforces in the sludge would increase deliquification and presetting inthe wedge zone. Thus, any improvements in the deliquifying andpresetting action in the wedge zone or elsewhere in a filter press wouldbe accepted and employed immediately.

The present invention is directed to the controlled adjustment of thewedge pressure in the wedge zone, the sealing of the marginal edges ofthe belts, as well as other techniques and structures for inducing thedeliquifying and presetting action in the wedge zone or otherwiseincreasing efficiency in the wedge zone.

SUMMARY AND OBJECTS OF THE INVENTION

The present invention relates to a belt filter press for dewatering ordeliquifying a material such as a sludge, slurry, fiber suspension,etc., the press having upper and lower belts which converge together ina wedge zone to compress, and thus deliquify, a material between thebelts in preparation for high pressure deliquification, belt supportsfor supporting the belts in the wedge zone, a cam assembly forcontrollably adjusting the wedge angle in the wedge zone by moving atleast one belt support while the belts are moving, and a cam actuatingdevice for actuating the cam assembly.

In the preferred embodiment, the cam assembly includes slide cam memberswhich are slideably movable relative to one another to narrow or widenthe wedge angle between the belts. The slideable movement of the slidecam members can be accomplished by two hydraulic cylinders or any othermeans which can function to move the slide cam members (such as steppingmotors) associated with a slide cam assembly on either side of the beltsupports, preferably the lower belt supports. The slide angle definedbetween the slide surfaces of the slide cam members preferablyapproaches a self-locking angle which provides stability to the relativeposition of the slide cam members, and thus the wedge angle. In thepreferred embodiment, the slide angle is approximately 10°, but can varydepending upon the materials used to construct the slide cam members,the expedient used to move the lower belt supports (hydraulic cylinderor other expedient), the weight of the lower belt supports, etc.

Also in the preferred embodiment, the lower belt supports includenumerous belt support members which are concave-like in shape.Preferably the lower belt support members have wedge-shaped endenclosure sections which force the marginal edges of the upper and lowerbelts upwardly, creasing the belts together where the wedge-shaped endenclosure sections meet the medial support section. This not onlyfacilitates the sealing of the marginal edges of the belts to preventmigration of the material being deliquified, but also aids in defining aconfined pocket in which the material to be deliquified is worked duringthe sinusoidal or undulated movement through the wedge zone. Thusanother feature of the preferred embodiment is to alternately andoppositely arrange the upper and lower belt supports or belt supportmembers such that a sinusoidal shearing action is imparted to thematerial held between the belts.

Still further, in the preferred embodiment, the marginal edges of theupper and lower belts are sealed at the beginning of the wedge zone,prior to a concave-like shaped lower belt support member, or throughoutthe wedge zone by sludge retaining wheels. The sludge retaining wheelscan be adjustably positioned against the upper and lower belts and/orspring-biased against the upper and lower belts to seal the marginaledges of the belts.

Yet another feature of the preferred embodiment is directed to theuniform movement of both sides of the lower belt support members, orupper belt support members as the case may be, through the use of anysuitable means, such as a rack and pinion assembly operativelyassociated with the hydraulic cylinders and slide cam assemblies oneither side of the lower belt support members.

Although many of the above features are incorporated into the preferredembodiment, the present invention is also directed to many of thesefeatures independently or in conjunction with one another, as indicatedin the claims and otherwise by the nature of the invention disclosedherein. The same is true of that aspect of the present invention relatedto the method.

Thus the present invention also relates to a method of deliquifying amaterial in a belt filter press having upper and lower belts convergingtowards one another in a wedge zone, including the steps of arrangingupper and lower belt support members alternately and oppositelythroughout at least a portion of the wedge zone, moving the upper andlower belts through the wedge zone in a shear inducing sinusoidalmanner, and adjusting the wedge angle during the movement of the upperand lower belts by moving at least one of the upper or lower beltsupports to narrow or widen the wedge angle.

In the preferred method, the marginal edges of the upper and lower beltswill be forced in an upward direction to provide a substantially sealedarrangement at the marginal edges and to form a substantially confinedpocket of material to be deliquified. The preferred method alsocontemplates the use of supplemental sealing means in the form of sludgeretaining wheels at at least the beginning of the wedge zone. Inaddition, the step of uniformly moving at least one of the beltsupports, preferably the lower belt support during adjustment of thewedge angle is provided. In the preferred embodiment, the means formoving at least one of the belt supports in a uniform manner is rack andpinion assemblies on either side of the belt support to be moved.

Accordingly, it is an object of the present invention to increase theefficiency of deliquifying and presetting the thickness and consistencyof a sludge in a wedge zone or elsewhere in a belt filter press.

It is another object of the present invention to provide for thecontrolled adjustability of the wedge pressure in the wedge zone.

It is another object of the present invention to provide belt supportswhich facilitate the sealing of the marginal edges of the belts, andfacilitate the inducement of an advantageous shearing action in thesludge during deliquification.

It is another object of the present invention to provide sealing meansand a method for sealing the marginal edges of the belts before enteringthe wedge zone and/or throughout the wedge zone.

It is another object of the present invention to provide a method ofdeliquifying sludge by inducing a shearing action for massaging a sludgein addition to merely compressing it.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects of the present invention will becomeapparent, as will a better understanding of the concepts underlying thepresent invention, by reference to the description which follows andrefers to the accompanying drawings in which:

FIG. 1 is a side elevational view of a belt filter press in accordancewith the present invention;

FIG. 2 is an enlarged side view of the wedge zone in FIG. 1, the beltsbeing in partial section;

FIG. 3 is an enlarged sectional view taken on line 3--3 of FIG. 2,illustrating in particular the upper and lower belts surrounding asludge and being sandwiched by the upper belt support bar and the lowerbelt support bar;

FIG. 4 is an enlarged partial side sectional view of the upper and lowerbelt support bars taken on line 4--4 of FIG. 3, illustrating inparticular the staggered arrangement of such support bars and sinusoidalclamshell path of the upper and lower belts and sludge therebetween;

FIG. 5 is an enlarged partial upstream view of the edge sealing wheelshown in FIGS. 1 and 2;

FIG. 6 is a plan view of the wedge zone shown in FIGS. 1 and 2;

FIG. 7 is an enlarged side view of a wedge zone and edge sealing wheelsin accordance with another embodiment of the present invention, thebelts being in partial section;

FIG. 8 is an enlarged upstream view of one of the edge sealing wheelshown in FIG. 7; and

FIG. 9 is a side elevational view of a belt filter press in accordancewith another embodiment of the present application, illustrating theapplication of the adjustable wedge on a two belt system.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, a belt filter press generally designated as 10 inaccordance with the present invention is illustrated. The belt filterpress 10 includes a gravity drainage belt 11 which is supported, at itstop flight, by a series of small rollers 12, and is carried by rollers13, 14, 15 and 16. The belt 11 is adapted to receive a sludge 17 on theupstream side of the top flight of belt 11. If necessary, the sludge 17will have been flocculated prior to being fed onto belt 11. As thesludge 17 is conveyed along the top flight of belt 11, free water drainsthrough the belt 11 into liquid collecting trays (not shown), whichcarry and dispose of the drained liquid. The drainage of the free waterin sludge 17 and the distribution of the sludge across the belt 11 isfacilitated by plow assemblies (not shown) and churning devices (notshown).

As the sludge 17 reaches the downstream side of the top flight of belt11, at roller 13, it drops the sludge 17 onto a lower belt 18 whichcooperates with an upper belt 19 in the wedge zone, generally designatedas 20, and in the high pressure zone, generally designated as 21. Asshown in FIGS. 1 and 2, lower belt 18 converges with upper belt 19 inthe wedge zone 20 to sandwich the sludge 17, and the belts 18 and 19enter the high pressure zone 21 together as they are wound aroundperforated drum 22.

The upper and lower belts 18 and 19, together with the sludge 17, arethreaded through the high pressure zone 21 around perforated drums 23,24 and 25, throughout which medium to high pressure deliquifying occursaround the perforated drums. Again, the liquid drained from the sludge17 in the perforated drum area is carried off by pans and otherstructures not shown. As can be appreciated, as the perforated drumsbecome smaller, the pressure imparted to the upper and lower belts 18and 19 increases, thus progressively compressing sludge 17 to deliquifythe same. From perforated roller 25, the upper and lower belt sandwichis wound around a series of solid rollers 26, 27, 28 and 29, throughoutwhich very high pressure is imparted to the upper and lower belts tofurther compress and deliquify such sludge 17.

Upon leaving the high pressure zone 21, after a partial winding aroundroller 29, the lower belt 18 and upper belt 19 are separated. The sludge17, now in the form of substantially dried cake 30 follow, in mostcases, the lower belt 18. The dried sludge or cake 30 are scraped fromthe lower belt 18 by doctor blade 31, and any residual dried sludge orcake on the upper belt 19 are similarly scraped off by the use of doctorblade 32.

After separation from the upper belt 19, the lower belt 18 returns tothe downstream side or discharge side of the gravity drainage zone toreceive additional sludge. The lower belt 18 is thus wound through aseries of rollers 33, 34, 35, 36 and 37. The upper belt 19 returns tothe beginning of the wedge zone 20 or prior to the beginning of thewedge zone 20, through a series of rollers 38, 39, 40 and 41. Both thelower belt 18 and the upper belt 19 may, in their separate flights, passthrough washing assemblies (not shown) through which the belts arewashed. Also, conventional devices used in belt filters, such asgravity, lower and upper belt take-up assemblies and gravity, lower andupper belt steering assemblies, can be employed in the belt filter press10.

Referring generally to FIGS. 1 and 2, and more specifically to FIGS. 4and 6, the wedge zone 20 includes, in the preferred embodiment, fiveupper belt support members 42 which extend cross-wise the upper belt 19and are fixed to upper frame 43, the upper frame 43 being pivotallyconnected to a machine frame at pivot 44. As shown in FIG. 6, the upperframe 43 includes three length-wise support bars, two cross-wise endbars and five cross-wise channel members which carry the upper beltsupport members 42. The upper belt support members 42 are fixed inposition, but may be in the form of rollers fixed to the upper frame 43so as to be rotatable with the upper belt 19. In such an embodiment, thefrictional drag of the upper belt 19 provides rotational energy torotate the rollers. Also, the upper belt support members 42 can be ofany other shape or structure suitable for purposes of supporting theupper belt 19 in the desired position.

The upper frame 43 also carries upper frame adjustment bolts 45 whichare associated with machine frame 46. The upper frame adjustment bolts45 enable the pivotal adjustment of the upper frame 43, and thus theupper belt support members 42. As a result, the wedge angle can bepreset for a particular range of angles through which the lower beltsupport members is movable, as explained below. In the preferredembodiment, the mechanical adjustment via the upper frame adjustmentbolts 45 is normally accomplished while the filter press is not running,as opposed to the adjustment of the lower belt support members which canbe accomplished while the filter press is operating to deliquify asludge. Thus, to mechanically adjust the upper frame 43, the upper frameadjustment bolts 45 are turned with a wrench. Of course, any suitableexpedient for mechanically adjusting the upper frame 43, and thus theupper belt support members 42, can be incorporated in the belt filter10. The present invention also contemplates automatic adjustment of theupper frame 43 and upper belt support members 42, if such automaticadjustment is desired.

The upper frame 43 also carries wheel supports 47 in which fork members48, carrying the sludge retaining wheels 49, are slideably disposed. Thefork members 48 include several holes, as do the wheel supports 47, andpins 50 are used to adjust the position of the sludge retaining wheels49 against the marginal edges of the upper belt 19 and lower belt 18. Asmost clearly shown in FIG. 5, the sludge retaining wheels 49 haveinteriorly bevelled edges to facilitate the sealing of the belt edges,although such bevelled edges are not required to seat the edges. Theweight of the wheels 49 and the adjusted position of the same providefor the sealing of the edges of the belts so that a higher wedgepressure can be established to thereby facilitate a greater degree ofdeliquification and presetting of the sludge.

The sludge retaining wheels 49 can be attached to upper frame 43 by aspring-biased system, such as that shown in the embodiment at FIGS. 7and 8. Also, any suitable expedient can be employed to seal the marginaledges of the belts in any desired area.

Lower belt 18 is supported by a series of lower belt support members 51and 56, of which there are seven in the preferred embodiment. The numberof support bars can be more or less depending upon the size of machineand application. The lower belt support members 51 are carried by alower frame 52 which is pivotally connected to a machine frame at pivot53. Each of the lower belt support members 51, as best shown in FIG. 3,is constructed with a center section 54 (or medial support section 54)and outer end closure sections 55, to form a concave-like surface onwhich the lower belt 18 and the upper belt 19 can rest. The outer endclosure sections 55 are wedge-shaped such that they increase inthickness from the center section 54 outwardly. The outer end closuresections 55 include a flat support surface 55a which is flanked bybevelled edges 55b to facilitate a smooth transition of the beltsdownward from the flat support surface 55a.

The outer end closure sections 55 facilitate the sealing of the beltedges, as well as the formation of a confined pocket of sludge which issubjected to a sinusoidal shear-inducing action in the wedge zone 20,which is discussed below and shown more clearly in FIG. 4. The outwardincline of the outer end closure sections 55 facilitate the sealing ofthe upper belt 19 and lower belt 18 at the marginal edges thereof, asshown in FIG. 3. This sealing effect is established by the weight of theupper belt on the lower belt and the weight of the belts being directedtowards the change in direction of the belts to thus form a creasebetween the center section 54 and outer sections 55, and prevents thesludge 17 from migrating through such creased area and up the incline ofthe flat support surface 55a.

It is noted that the sealing effected by the end closure sections 55 isshown in FIG. 1 where the edges of the belts are illustrated togetherand the thickness of the belts and sludge between the upper beltsupports 42 and the center section 54 of the lower belt supports 51 isalso shown. In FIGS. 2, 4 and 7, however, the belts are shown in partialsection so that the sinusoidal or undulating action of the belt can bebetter visualized.

The incline of the outer end closure sections 55 can be any suitableangle, depending in part on the structure of the belts being used. Ifthe incline is too steep, the belts may be distorted; whereas tooshallow an angle will not effect enough of a change in the crosswisedirection of the belts to create an effective seal for a givenapplication. In the preferred embodiment, the incline of the outer endclosure sections 55 is approximately 18°, but other suitable angles willalso be effective.

As shown in FIGS. 1 and 2, the downstream or lowermost lower beltsupport 56 is of a structure similar to the upper belt support members42. Once again, the lower belt support members 51 and 56 are fixed inposition, but can be arranged so that they or portions thereof arerotatably connected to lower frame 52. In this regard, the lower beltsupport members 51 can be made up of a central cylindrical memberflanked by outwardly inclined cylindrical members, or any other suitablestructure or arrangement consistent with the principles of the presentinvention.

A tapered slide cam assembly 57, shown in FIGS. 1 and 2, is associatedwith both sides of the lower frame 52. Each tapered slide cam assembly57 includes an upper slide cam member 58 connected to the lower frame 52and a lower slide cam member 59 which is slideably associated with upperslide cam member 58. In the preferred embodiment, the upper and lowerslide cam members 58 and 59 are made of a high molecular weightpolyethylene, which is a relatively durable material. The upper andlower slide cam members 58 and 59 include slide surfaces which togetherdefine a slide cam angle, as measured from an imaginary horizontalplane. Preferably, the slide cam angle preferably approximates aself-locking angle which can vary depending upon the weight of the lowerframe 52, the coefficient of friction between the slide surfaces of theupper and lower slide cam members 58 and 59 (preferably low), theexpedient for moving the lower slide cam member 59, etc. The shallowangle of the tapered slide cam assembly 57 is intended to help maintainthe appropriate wedge angle and associated wedge pressure shoulddrifting occur in the hydraulic cylinders or for any other reason. Atrue self-locking angle, to the extent definable with certainty, may notbe possible in certain applications or in any application. That theangle used approaches a self-locking angle to provide holding andstability is enough. In connection with the preferred embodiment, theslide cam angle which provides the appropriate attributes isapproximately 10°. However, the slide cam angle can be in a range from8° to 15°, or even outside of this range, depending upon the above-notedparameters and the degree of stability required.

Each lower slide cam member 59 is connected to a hydraulic cylinder 60on each side of the lower frame 52, although it is possible to employjust one hydraulic cylinder or other device to raise or lower both sidesof the lower frame 52. In addition, as shown in FIG. 6 each hydrauliccylinder 60 is connected to machine frame 46 at one end, and machineframe 61 at the other end and is adapted to move linearly in order tomove the respective lower slide cam member 59. The lower slide cammember 59, in turn, slides against the respective upper slide cam member58 to pivotally move the lower frame 52 (and thus the lower belt supportmembers 51) about pivot 53. Of course, this movement varies the wedgeangle formed between the lower belt support members 51 and the upperbelt support member 52, and thus varies the wedge pressure exerted onthe lower belt 18 and upper belt 19.

In addition, although the preferred embodiment calls for the cylinders60 to be actuated hydraulically, any other appropriate means ofactuation, such as pneumatic actuation or electrical stepping motor, iscontemplated herein. In this context, the means for moving the lowerframe 52 need not be a cylinder, but can be any suitable expedient,again for controllably adjusting the wedge angle in the wedge zone 20.The advantage in using hydraulics is that hydraulics provides a positivecontrol of the cylinders, and thus the movement of the lower frame 52.

In addition, as shown in FIG. 2 each hydraulic cylinder 60 is associatedwith a rack and pinion assembly comprising a rack 62 connected to thehydraulic cylinder 60, and a pinion gear 63. Of particular importance isthe association of the pinion gears 63 on either side of the wedge zone20. A shaft extending cross-wise under the wedge zone 20 connects therespective pinion gears 63 to help keep the tapered slide cam assemblyin alignment. The pinion gears 63 and associated shaft make up for anydeviance or drag in the hydraulic cylinder 60 which might result in oneside of the lower frame 52 being moved higher or lower than the otherside. The lower frame 52 and lower belt support members are thus squaredand moved uniformly through the use of the rack and pinion assemblies.

The staggered arrangement of the upper belt support members 42 and thelower belt support members 51 is of particular importance in connectionwith a preferred embodiment of the present invention. As shown in FIG.4, the staggered arrangement of the support members in the wedge zone 20provides a serpentine or sinusoidal clamshell effect as the beltsundulate around the upper and lower belt supports in the wedge zone 20.This arrangement of the upper and lower belts 18 and 19 as they carrythe sludge 17 is significant because of the action imparted to the upperand lower belts 18 and 19 during the movement of such belts through thewedge zone 20. Thus, the upper and lower belts 18 and 19 not onlyconverge towards one another in the wedge zone 20, but because of thestaggered arrangement of the upper belt support members 42 and lowerbelt support members 51, the belts gently massage and squeeze the sludge17 throughout the wedge zone 20. This gentle massaging of the sludge 17helps efficiently deliquify the same in the wedge zone 20 by impartingshear forces in several directions within the sludge 17.

The shear-inducing effect is of particular help in deliquifying thesludge 17 when the lower belt support members 51 are generally concavein shape, as shown in FIG. 3 in accordance with the preferredembodiment. It is the concave-like shape, established by thewedge-shaped outer sections 55, which concentrates the sludge 17 in thecentral portion of the belts 18 and 19, effectively forming a confinedpocket. This confined pocket arrangement does not permit the sludge 17to simply be displaced between the belts; rather, the shear forcesimparted to the sludge 17 continuously change directions in the confinedpocket of sludge to provide for the highly effective deliquifying andpresetting of the sludge 17.

FIGS. 7 and 8 illustrate another embodiment of the present invention,wherein the lower belt support members 151 are all of a similarconstruction to the upper belt support members 142. Thus, because thereis no outward incline near the marginal edges of the belts 118 and 119,sealing wheels are provided throughout the length of the wedge zone 120.In this embodiment, the sludge retaining wheels 149 are connected to aframe support 147 via a spring-biasing assembly 190 which is connectedto the sludge retaining wheel 149 via a fork member 148. Thespring-biasing assembly permits the sludge retaining wheel 149 to moveup and down to maintain an appropriate seal on the marginal edges of thebelts 118 and 119.

Of course, the stiffness of the spring used in the spring-biasingassembly 190 will affect the extent to which the sludge retaining wheel149 exerts pressure against the upper belt 119 and the lower belt 118,and the extent to which the upper and lower belts can move up and down.

In another embodiment of the present invention, shown in FIG. 9, theadjustable wedge can be employed on a two-belt filter press, whereby theupper belt serves as the gravity drainage belt as well as the upperpressure belt. Of course, yet further applications of the adjustablewedge is contemplated.

In the preferred embodiment, the hydraulic cylinder 60 is actuated by ahand valve 64 on panel 65, which provides various controls to operatethe belt filter press 10 (such as take-up and steering). From a pointadjacent to the control panel 65, an operator can view the belts 18 and19 as they converge in the beginning of the wedge zone 20. The operatorcan see the sludge 17 bulging under the upper belt 19, and can ascertainhow uniformly distributed the sludge 17 is between the belts 18 and 19.Thus, the operator can adjust the wedge angle, and therefore the wedgepressure, by actuating the hydraulic cylinder with hand valve 64. In oneposition, the hand valve 64 moves each of the cylinders 60 linearlytowards the upstream side of the belts 18 and 19, which causes thethicker portions of the slide cam members 58 and 59 to move together toraise the lower frame 52 and lower belt support members 51. This narrowsthe wedge angle. The operator would adjust the wedge angle in thismanner when he viewed a mass or bulge of sludge 17 in the center of thebelts 18 and 19. Thus, the wedge pressure would be increased, and thesludge 17 would be compressed and forced outwardly towards the marginaledges of the belts 18 and 19.

If the operator sees that the sludge 17 is becoming very close to themarginal edges of the belts 18 and 19, or even spilling out of suchedges, he will move the hand valve 64 into the opposite position,whereby each of the cylinders 60 would move linearly in the downstreamdirection. This causes the narrow portions of the slide cam members 58and 59 to come together to lower the lower frame 52 and lower beltsupport members 51. This widens the wedge angle. This results in thewedge pressure being decreased.

An operator might also inspect or examine other portions of the beltfilter press 10 as it is running in order to ascertain whether the wedgeangle should be increased or decreased. One such area he may view is theperforated drum area to determine whether the sludge 17 is too wet as itexits the wedge zone 20. In addition, the wedge angle may be adjustedautomatically, whether a manual operator is present or in the stead ofsuch a manual operator. Such automatic wedge adjustment can beestablished by a number of different expedients, which can be used aloneor together.

For instance, sensors can be provided along the marginal edges of thebelts 18 and 19 to ascertain whether there is any migration of thesludge 17. The sensors could send information to a control panel tocontinuously and automatically adjust the wedge angle. Alternatively,sensors or strain gauges might also be placed cross-wise on a sensor barin the area of the wedge zone to ascertain the distribution of thesludge 17 across the belts 18 and 19. Also, sensors which determine thewetness, viscosity, density or other characteristics of the sludge 17itself might be employed to automatically and continuously set thecylinders 60, thus adjusting the wedge angle and wedge pressureappropriately.

Still further, a sludge level sensor can be provided to automaticallyadjust the wedge angle and wedge pressure. Such a sludge level sensorcould provide a milliamp signal to a servo valve or valves which would,in turn, control the movement of the cylinders 60. The cylinders 60would move in the appropriate direction depending upon the signal beinggenerated by the sludge level sensor to raise or lower the lower frame52 to narrow or widen the wedge angle.

In operation, the sludge 17 is controllably and lightly compressed andmassaged in the wedge zone 20 in order to prepare the sludge 17 for thehigh pressure zone 21. The belts 18 and 19, and the sludge 17 sandwichedtherebetween, winds through a series of staggered and converging upperand lower belt supports, imparting a sinusoidal shearing action to thesludge 17 in the confined pocket. This sinusoidal shearing action gentlymassages the sludge 17 in the confined pocket as the sludge 17 iscontinuously compressed such that the thickness of the sludge 17 at theentrance of the wedge zone 20 is greater than the thickness of thesludge 17 at the exit of the wedge zone 20. Thus, the sludge undergoesnot only a wedge-type compression in the wedge zone 20, but is alsocontinuously subjected to a massaging treatment which gently squeezesliquid from the sludge 17. This differs from a conventional wedge-typecompression in that the shear forces which result in deliquification areestablished in different directions within the sludge 17 in the confinedpocket and continuously change direction as the sludge 17 winds throughthe converging belt supports in a serpentine fashion.

In addition to the above, greater pressure can be applied to the sludge17 the wedge zone 20 by sealing the marginal edges of the belts 18 and19. This permits great efficiency in preparing the sludge 17 for thehigh pressure zone 21, since more liquid can be removed from the sludge17 prior to entering the high pressure zone 21. Therefore, higherpressures can be used more quickly in the high pressure zone 21, andhigher pressures can be obtained at the end of the high pressure zone21. The result is a drier sludge cake.

While the foregoing description and figures illustrate the preferredembodiments of the belt filter press and separation method in accordancewith the present invention, it should be appreciated that certainmodifications can be made and are encouraged to be made in thestructure, materials and techniques of the disclosed embodiment withoutdeparting from the spirit and scope of the present invention which isintended to be captured by the claims set forth immediately below.

It is claimed:
 1. A belt filter press for deliquifying a material, saidbelt filter press comprising:a. a lower belt having a first path oftravel and an upper belt having a second path of travel, said lower andupper belts traveling together and converging towards one another in awedge zone through which a material is progressively compressed betweensaid lower and upper belts, the angle of convergence between the lowerand upper belts defining a wedge angle which corresponds to the degreeof pressure exerted on the material in the wedge zone; b. a lower beltsupport for supporting said lower belt in said wedge zone and an upperbelt support for supporting said upper belt in said wedge zone; and c. abelt support moving device for moving at least one of said belt supportswhile said lower and upper belts are moving in said respective first andsecond paths of travel in order to adjust the wedge angle in the wedgezone without stopping the movement of the material in the wedge zone,said lower belt support including lower belt support members extendingcross-wise below and in contact with said lower belt, said upper beltsupport including upper belt support members extending cross-wise on topof said upper belt, said lower and upper belt support members beingalternately and oppositely arranged in at least a portion of said wedgezone so that the upper and lower belts and the material therebetween arethreaded through said respective support members in a shear-inducingserpentine manner, resulting in the material between said belts beingmassaged in addition to being compressed in the wedge zone.
 2. The beltfilter press in claim 1, wherein at least a portion of said lower beltsupport members includes a medial support section flanked by two endclosure support sections, said end closure support sections extendingupwardly and outwardly from said medial support section, whereby themarginal edges of said lower and upper belts lie in a substantiallysealed arrangement on said end closure support sections.
 3. A beltfilter press for deliquifying a material, said belt filter presscomprising:a. a first belt having a first path of travel and a secondbelt having a second path of travel, said first and second beltstraveling together and converging towards one another in a wedge zonethrough which a material is progressively compressed between said firstand second belts, the angle of convergence between the first and secondbelts defining a wedge angle which corresponds to the degree of pressureexerted on the material in the wedge zone; b. a first belt support forsupporting said first belt in said wedge zone and a second belt supportfor supporting said second belt in said wedge zone, at least one of saidbelt supports being movable while said first and second belts are movingin said respective first and second paths of travel in order to adjustthe wedge angle in the wedge zone without stopping the movement of thematerial in the wedge zone; and c. at least one sludge sealing devicefor sealing the marginal edges of said first and second belts in thearea of said wedge zone, said sludge sealing device substantiallypreventing the migration of the material between said first and secondbelts by bringing the marginal edges of the belts together tosubstantially contain the material between the belts.
 4. The belt filterpress in claim 3, wherein said sealing device comprises at least onesludge retaining wheel at each marginal edge of the first belt.
 5. Thebelt filter press in claim 4, wherein more than one sludge retainingwheel is provided on each marginal side of said first belt, and saidmore than one sludge retaining wheels are disposed from the upstreamside of said wedge zone to the downstream side of said wedge zone. 6.The belt filter press in claim 4, wherein said sludge retaining wheelsare provided at the beginning of said wedge zone at a point prior tosaid belt supports.
 7. The belt filter press in claim 3, wherein said atleast one sludge sealing device is adjustably disposed on said firstbelt.
 8. The belt filter press in claim 3, wherein said at least onesludge sealing device is spring-biased against said first belt.
 9. Thebelt filter press in claim 3, wherein said first belt is an upper belt,said second belt is a lower belt, said first belt support is an upperbelt support and said second belt support is a lower belt support, andwherein said lower belt support includes lower belt support membersextending cross-wise below and in contact with said lower belt, saidsealing means comprising end closure support sections on at least aportion of said lower belt support members, said end closure supportsections being connected by a medial support section, and said endclosure support sections extending upwardly and outwardly from saidmedial support section, whereby the marginal edges of said upper andlower belts lie in a substantially sealed arrangement on said endclosure support sections.
 10. The belt filter press in claim 9, whereinsaid sealing device also comprises at least one sludge retaining wheelat each marginal edge of the upper belt.
 11. The belt filter press inclaim 10, wherein said sludge retaining wheels are provided only at thebeginning of said wedge zone at a point prior to said belt supports. 12.A belt filter press for deliquifying a material, said belt filter presscomprising:a first belt having a first path of travel and a second belthaving a second path of travel, said first and second belts travelingtogether and converging towards one another in a wedge zone throughwhich a material is progressively compressed between said first andsecond belts, the angle of convergence between the first and secondbelts defining a wedge angle which corresponds to the degree of pressureexerted on the material in the wedge zone; b. a first belt support forsupporting said first belt in said wedge zone and a second belt supportfor supporting said second belt in a said wedge zone, there being afirst side of said first and second belt supports and there being asecond side of said first and second belt supports, at least one of saidbelt supports being movable while said first and second belts are movingin said respective first and second paths of travel in order to adjustthe wedge angle in the wedge zone; and c. a belt support adjustmentdevice associated with said first side and said second side to providefor simultaneous movement of said first and second sides of said beltsupports, said belt support adjustment device being operable touniformly move said first and second sides of said belt supports duringadjustment of the wedge angle and without stopping the movement of thematerial in the wedge zone.
 13. The belt filter press in claim 12,wherein said means for uniformingly moving said at least one of saidbelt supports during adjustment of the wedge angle is a first rack andpinion assembly associated with said adjustment means at said first sideand a second rack and pinion assembly associated with said adjustmentmeans at said second side, said first and second rack and pinionassemblies being operatively associated so as to ensure uniform movementof said at least one of said belt supports during adjustment of thewedge angle.